1. Field of the Invention
The present invention relates to a seat lifter for lifting and lowering a seat, such as an automobile seat, and a seat having the seat lifter.
2. Description of the Related Art
Heretofore, there has been widely known a seat lifter which comprises a lifting and lowering mechanism section for lifting and lowering a seat. For example, such a seat lifter is disclosed in Japanese Utility Model Laid-Open Publication No. 60-164439.
A seat lifter disclosed in Japanese Utility Model Laid-Open Publication No. 60-164439 comprises: right and left links each rotatably coupled to a respective one of two right and left base members and further to a respective one of two right and left seat frames disposed just above the respective base members, wherein the right and left links are coupled to each other through a shaft (coupling member); and a single lifting and lowering mechanism section adapted to lift and lower the right seat frame with respect to the right base member. The lifting and lowering mechanism section includes a sector gear rotatably attached to a longitudinally central region of an inner surface of the right seat frame, a coupling rod coupling the right link and the sector gear, and a center gear meshed with the sector gear.
The center gear is adapted to be manipulatively rotated so as to swingably move the right link through the sector gear and the coupling rod, whereby the right seat frame is lifted or lowered with respect to the right base member. On the other hand, the left seat frame is adapted to be lifted or lowered in such a manner that it is pushed upwardly or downwardly by an end of the shaft moved along with the lifting or lowering of the right seat frame.
However, in the seat lifter as disclosed in Japanese Utility Model Laid-Open Publication No. 60-164439, only the right seat frame is manipulatively lifted or lowered by the lifting and lowering mechanism section composed of the sector gear, the coupling rod and the center gear, and the left seat frame is lifted or lowered in such a manner that it is pushed upwardly or downwardly by the end of the shaft moved along with the lifting or lowering of the right seat frame. Thus, it is difficult to adequately lift and lower the left seat frame, which causes a problem of difficulty in smoothly lifting and lowering a seat
It is an object of the present invention to provide a seat lifter capable of smoothly lifting and lowering both right and left seat frames with respect to respective base members so as to allow a seat to be smoothly lifted and lowered, and further provide a seat having the seat lifter.